​It be a month before I can afford to buy one but I thought I would go ahead post now just in case I can't get the engine finished in time to plow my garden. I'm looking for a running briggs and stratton engine for my SS15.

The 9-12 will do the job just fine but I would still go with the original size 32 cube engine. Physically the 9-16 are all the same size. The 12 does have a counter balancer sticking out on the PTO side of the block that could be an issue.